Senator Lindsey Graham once said Donald Trump should "go to hell." Trump called him a "nut job." Today, they are unlikely political allies, with the powerful South Carolinian influencing the president on multiple fronts.
While they got off on the wrong foot, the Republican lawmaker has emerged as a crucial Trump collaborator, even if they remain at odds on some prominent issues.
On immigration, tensions with Saudi Arabia, criminal justice and the partial government shutdown now in its fourth week, Graham has repeatedly weighed in, not just in public fora but behind closed doors with Trump.
And as the Senate Judiciary Committee's new chairman, the often audacious Republican will be able to again showcase his support for Trump's nominees on Tuesday, when his panel begins hearings on Bill Barr, the president's nominee to become attorney general.
But is the straight-talking, critic-turned-ally also a so-called "Trump whisperer" who can help the president navigate Washington's pitfalls?
"That's what I think of whenever I think of Lindsey," Republican Senator Mike Rounds told AFP about the moniker, which has circulated ever since Graham started golfing with Trump in 2017 despite their differences.
"He's one of the guys who can go in and sit down and have a frank discussion with the president."
Those discussions do not always go Graham's way. On Monday, Trump dismissed the senator's effort to allow closed-down government agencies to re-open while a debate proceeds over border security and immigration.
"That was the suggestion that Lindsey made, but I did reject it," Trump told reporters at the White House.
- 'This is hell' -
When Graham's gavel bangs early Tuesday, it will cement his role as a Capitol Hill power player.
The senator has said he wants a respectful hearing, after Democrats expressed worry about Barr's criticism of the accusations of collusion between Trump and Russia.
Graham's fiery indignation against Democrats in another forum last year -- Supreme Court nominee Brett Kavanaugh's hearing -- made him a conservative rock star.
"This is not a job interview. This is hell," Graham thundered after losing patience with Democrats who grilled Kavanaugh about sexual assault allegations from decades ago.
"You all want power. God, I hope you never get it," he seethed, pointing his finger at stone-faced Democrats.
Kavanaugh was eventually confirmed to the high court, a huge victory for the White House, which sang Graham's praises.
Graham's performance may have had a political calculation. He is up for re-election in 2020, and should he appear too centrist or if Trump turns against him, he could face a difficult primary challenge from the right.
Graham, whose own 2016 presidential campaign was short-lived, spit venom at Trump during the race, calling him a "kook" unfit for office.
In 2017 he would savage Trump for his bombastic tweets, and he criticized the president's weak response to a violent white supremacist rally in Virginia.
But he also insisted Trump was growing into the job. They played golf, dined at the White House and spoke often by phone.
- Congressional confidante -
As a national security hawk, Graham operated in lockstep with his best friend in the Senate, the late John McCain, on major issues like Iraq and campaign finance reform.
McCain never warmed to Trump, and clashed bitterly with him on issues like health care, awkwardly putting Graham on the opposite side of key votes.
But with McCain away from Washington for much of 2018 due to illness -- he died in late August -- Graham inched closer to Trump's orbit.
"If you know anything about me, I want to be relevant," Graham told CNN days after McCain's death.
"I want to make sure that this president, Donald Trump, who I didn't vote for, ran against, is successful."
Eventually he became a congressional confidante, and was looked to multiple times to broker deals on immigration. Those deals have yet to bear fruit, but Graham remains at the center of the negotiations.
He has also publicly pushed back against the president on foreign policy.
In December he severely criticized Saudi Arabia's crown prince Mohammed bin Salman over the murder of a US-based journalist in the Saudi consulate in Turkey.
And he bluntly urged Trump to reconsider his decision to pull US troops out of Syria.
Republican colleagues nevertheless sound pleased with the relationship.
"It's been a positive," Senator Marco Rubio said.
Graham and Trump do not see eye to eye on everything, Rubio added, "but I'm glad Lindsey's talking to him about things."
On the Democratic side, Senator Cory Booker said he was happy that Graham's "relationship with the White House helped" bring about a major reform of the criminal justice system.
Graham has been in Congress since 1995, often showing a self-deprecating humor.
As a single male, he has faced rumors about his sexuality. Last October he told celebrity website TMZ: "To the extent that it matters, I'm not gay."